Manufacture of wrought iron



Patented Dec. 27, 1938 UNITED STATES MANUFACTURE OF WROUGHT IRON EdwardB. Story, Library, Edgeworth, Pa., assignors and Evard P. Best, to A. M.Byers Company, Pittsburgh, Pa, a corporation of Pennsylvania No Drawing.Application May 26, 1937, Serial No. 144,920

4 Claims.

The present invention relates to the manufacture of wrought iron, andmore particularly to an improvement in the Aston process in which apreviously formed molten refined iron is mixed '5 in comminuted formwith a previously formed molten slag to form a wrought iron ball, whichis then handled in the usual way to expel the surplus slag and producethe product known as Wrought iron. We have found that the addition of anefiective amount of aluminum to the refined metal, prior to theincorporation of the slag, produces a marked improvement in the process,particularly in the control of the slag content and its distribution inthe finished product. The wrought iron also has an increased tensilestrength and a lessened susceptibility to aging.

The invention will be described with particular reference to itsembodiment in the'present commercial practice of making wrought iron inaccordanoe with the Aston process. In such commercial practice, the ironis first blown in a Bessemer converter, the blowing being continued at arelatively high temperature until the iron is full-blown. The blownmetal from the Bessemer converter is poured into a transfer ladle, fromwhich it is in turn poured into the ladles of the shotting machines,which serve topour the molten refined iron into receptacles containingmolten iron-silicate slag, known as processing slag. Through acombination of physicochemical reactions involving metal solidificationand relative gas solubilities of the metal in the molten and solidconditions, the molten refined metal is disintegrated into a comminutedform to form a spongy mass of iron and slag, which collects at thebottom of the slag receptacle. This ball or mass of commingled iron andslag is removed and squeezed to expel the surplus slag. It is thensubjected to the usual rolling operations to produce products such asbars and plates which have the well known fibrous structurecharacteristic of Wrought iron.

It has been recognized that in the best Wrought iron the slag fibresshould be thin and uniformly distributed. In the commercial manufactureof wrought iron, as heretofore carried out, it has been difiicult touniformly secure the desired fineness and uniform distribution of theslag fibres, and it is frequently necessary to roll the iron to bar formand repile and reroll in order to secure a fine textured slagdistribution. Notwithstanding all these precautions the wrought iron hasoften displayed undesirably large individual slag pockets.

We have found that if an efiectiveamount of aluminum is added to therefined iron before it is dispersed in the processing slag, a finertextured and more uniform distribution of the slag is secured, and thatthe tendency to form large slag pockets order to be effective, thealuminum should be added in an amount of at least two pounds per ton ofthe Bessemer metal, but not exceeding fifteen pounds per ton, asaluminum in such high ranges adversely affects the Weldability of theWrought iron. The aluminum is added preferably from two to six poundsper ton, usually about four pounds per ton of the Bessemer metal.

In applying the invention to the usual com mercial operation of theAston process, the iron is first fully blown in a Bessemer converter inthe usual way and then poured into the transfer ladle. The iron is thenpoured from the transfer ladle into the ladles of the shotting machines.During such pouring the aluminum is added, preferably being thrown intothe stream of metal. The aluminum is preferably added in the form of a50% ferro-aluminum because of its greater specific gravity, thenecessary aluminum addition being figured on the basis of 50% aluminumin the term-aluminum. The refined metal to which the aluminum thus addedis then poured into the receptacles containing the separately formedmolten iron-silicate slag, as described for example in the Wille PatentsNos. 1,890,660 and l,933,5'l7.' As the stream of molten iron enters theslag, it is disintegrated and the iron in comminuted form is dispersedin the processing slag and settles through the slag to the bottom of thereceptacle forming a spongy mass. of iron and slag or ball, which isremoved, squeezed to expel the surplus slag and to weld the ironparticles together to form a bloom which is then rolled in the usualWay.

Since the full-blown iron is highly oxidized, the aluminum isundoubtedly substantially all converted into aluminum oxide. As is wellknown, the alumina inclusions formed in steel when aluminum is used as adeoxidizer are in a relatively fine state of dispersion. The aluminaparticles are highly iniusible and do not display a tendency to combinewith neighboring particles to form masses large enough to rise up andclear themselves of the metal. If the metal from the Bessemer converter,to which the aluminum has been added in relatively large amountsrequired in our process, were to be cast in ingot form, the amount ofalumina inclusions would undoubtedly be so great as to detrimentallyaffect, if not completely spoil, the metal. However, we have found thatunder the peculiar conditions obtaining in the Aston process in whichthe refined metal is mixed in comminuted form with the processing slag,such alumina inclusions are substantially eliminated from the iron. Theiron solidifies in the form of tiny individual particles, which presenta very large aggregate surface between the iron and the slag, so thatthe finely dispersed alumina particles are eliminated or issubstantially eliminated. In I washed from the metal by the slag and themetal itself shows little if any evidence of alumina inclusions. Sincethe metal is highly oxidized, the aluminum is substantially completelyoxidized and eliminated from the iron, the analysis of the iron showingat most but a trace of aluminum,

' when the preferred amount of about two to six pounds per ton ofaluminum is used.

The exact mechanism whereby the aluminum insures a more uniform andfiner textured slag distribution isnot at present fully understood.While the aluminum undoubtedly deoxidizes the metal to a large extent,deoxidation alone does not apparently account for the improvedproperties, since if the metal is deoxidized with the usual deoxidizers,silicon or manganese, the wrought iron is detrimentally affected. It maybe that the presence of the aluminum in the iron,

or the presence of the alumina which is expelled from the iron particlesas they solidify, affects the wetting action of the slag upon the iron.Whatever may be the reason, the slag appears to be more easily expelledfrom the ball in the press and exists in the form of finer and moreuniformly distributed fibres in the rolled product.

Tests have shown that if a refined heat of iron from the Bessemerconverter is divided into two portions, one of which is treated inaccordance with our process and the other untreated, and both portionsprocessed, pressed, rolled and otherwise handled in an identical manner,the wrought iron from that portion which was treated with aluminum willdisplay a substantial difierence in character from that produced fromthe untreated metaL'in that the fibrousness of the untreated metal willbe considerably more coarse in texture than that of the treated metal,and the slag fibres will be larger and willnot have the fine and uniformdistribution obtained in the 1 aluminum-treated metal. Also, the metaltreated with aluminum will have an increased tensile strength; forexample, if the untreated metal has a tensile strength of about 48,000pounds per square inch, the treated metal will have a tensile strengthof about 51,000pounds per square inch. The treated metal also has alower susceptibility to aging either by strain aging or quench aging.

While the addition of the aluminum is particularly advantageous to metalrefined in a Bessemer converter, the metal for making the wrought ironmay be otherwise refined, as in an open-hearth or electric furnace, inwhich case smaller amounts of aluminum may be required as the metal is.less oxidized.

While the amount of aluminum added is considerably greater than thatemployed in usual steel making practice to kill the steel in the ingotmolds, the amount of aluminum used is preferably less than thattheoretically required to completely deoxidize the Bessemer metal. Forexample, it would require about eight pounds of aluminum per ton tocompletely deoxidize the full-blown metal from the converter, whereas wefind that about four pounds of aluminum per ton is sufficient to givethe desired control of the slag distribution. When the hotter metal ispoured into the cooler slag as in the Aston process, the solidificationof the metal causes release of in cluded gas which results in adispersion of the metal into the slag in a finely comminuted form. Asthe finely comminuted iron particles become solidified, the solubilityof the iron oxide is greatly decreased and the iron oxide is expelled isfully efiective during the solidification of the iron and theformation'of the spongy mass or ball of iron and slag, since the iron isnot subjected to any continued or substantial oxidation between the timeof the aluminum addition and the solidification of the iron incomminuted form upon its incorporation into the slag. The aluminumaddition would be ineffective for the purpose of the present invention,if the Bessemer metal to which the aluminum is added were to be puddledin an iron-oxide-containing slag, since such pud-dling would result in areoxidation of the metal and the dissipation of the deoxidizing effectof the aluminum before the iron could come to nature and form a puddleball. While we prefer to form the ball by pouring the metal into areceptacle filled with molten slag, as described for example in saidWille patents, the iron may be otherwise incorporated into the moltenslag so long as the iron is not subjected to oxidizing treatment whichwould neutralize the efiect of the aluminumaddition.

While we have specifically described the preferred embodiment of ourinvention, it is to be understood that the invention may be otherwiseembodied and'practiced within the scope of the 7 following claims.

We claim:

1. The process of controlling the slag content and distribution in themanufacture of wrought iron, which comprises refining iron by blowing ina Bessemer converter, adding aluminum to the blown molten iron in theproportion of about two to six pounds of aluminum to 'a ton of iron,mixing the ironrin comminuted form with a separately formed molten slagto form aspongy mass of iron and slag, and expelling the surplus slagfrom such mass. a

2. The process of controlling the slag content and distribution in themanufacture of wrought iron, which comprises refining iron by blowing ina Bessemer converter, adding aluminum to the blown molten iron in theproportion of about two V proportion of about two to six pounds ofaluminum to one ton of iron, mixing the molten iron in comminuted formwith a separately formed molten slag to form a'spongy mass ofiron andslag, and expelling the surplus. slag from such mass.

4. The process of controlling the slag content and distribution in themanufacture of wrought iron, which comprises forming a molten refinediron, adding aluminum to the molten iron in the proportion of about twoto fifteen pounds of aluminum to one ton of iron, mixing the molten ironin comminuted form with a separately formed molten'slag to form a spongymass of iron and slag, and expelling the surplus slag from such mass. 1

' EDWARD B. STORY.

EVARD P. BEST.

